Variabilidad en la tasa de cesáreas entre hospitales públicos de Costa Rica / Variability in cesarean delivery care among Costa Rica public hospitals

Antecedentes: el porcentaje de cesáreas es un indicador multidimensional muy utilizado en el análisis del desempeño hospitalario porque aborda aspectos de adecuación de atención médica, seguridad del paciente y eficiencia en utilización de los recursos. Objetivo: determinar la utilización y medir la variabilidad de las tasas de cesárea en los hospitales públicos de Costa Rica. Método: se utilizaron datos de partos del período 2010-2011 para calcular las tasas de cesáreas en el total de partos y en partos de bajo riesgo. Se estimaron proporciones con sus intervalos de confianza para determinar cuáles hospitales se alejan significativamente del rango óptimo de cesáreas recomendado por la OMS y se calcularon rangos de variación tanto para las tasas de cesáreas, como de la estancia media de los procedimientos obstétricos. Resultados: la utilización de cesárea supuso el 19,4 por ciento del total de partos y 18,6 por ciento en partos de bajo riesgo. La mitad de los hospitales registra porcentajes de cesáreas fuera del rango recomendado por la OMS (10-15 por ciento). Existe una alta variabilidad en la tasa de cesárea entre centros hospitalarios y una variabilidad moderada en la estancia media de los procesos de cesárea y parto vaginal con complicaciones. Conclusión: las diferencias en la gravedad de las pacientes no influyen significativamente en la variabilidad de las tasas de cesáreas en los hospitales públicos de Costa Rica, dado que los centros con alta incidencia de cesárea de bajo riesgo tienen también alta incidencia en el resto de los partos.

Background: the cesarean rate is a multidimensional indicator very used in the performance hospital analysis because it includes aspects of adequacy of care, patient safety and efficiency in resource utilization. Objective: to determine the rates and variability in cesarean delivery care among Costa Rica public hospitals. Methods: we used data of births from the period 2010-2011 to calculate rates of cesarean in total and low-risk deliveries. Proportions and its confidence intervals were estimated to determine which hospitals are significantly away of cesarean optimal range recommended by WHO and variation ranges were calculated for both cesarean rates and the average stay of obstetrical procedures. Results: the cesarean rate in total deliveries was 19.4 percent and 18.6 percent in low-risk deliveries. Half of hospitals registered cesarean rates outside of the range recommended by WHO (10-15 percent). There is high variability in the rate of cesarean section between hospitals and moderate variability in the length of stay in the processes of cesarean and vaginal delivery with complications. Conclusion: the differences in the severity of the patients did not significantly influence the variability of cesarean rate, because hospitals with a high incidence of low-risk cesarean also have high rates on the rest of deliveries.

Proline antagonizes GABA-induced quenching of quorum-sensing in Agrobacterium tumefaciens.

Plants accumulate free L-proline (Pro) in response to abiotic stresses (drought and salinity) and presence of bacterial pathogens, including the tumor-inducing bacterium Agrobacterium tumefaciens. However, the function of Pro accumulation in host-pathogen interaction is still unclear. Here, we demonstrated that Pro antagonizes plant GABA-defense in the A. tumefaciens C58-induced tumor by interfering with the import of GABA and consequently the GABA-induced degradation of the bacterial quorum-sensing signal, 3-oxo-octanoylhomoserine lactone. We identified a bacterial receptor Atu2422, which is implicated in the uptake of GABA and Pro, suggesting that Pro acts as a natural antagonist of GABA-signaling. The Atu2422 amino acid sequence contains a Venus flytrap domain that is required for trapping GABA in human GABA(B) receptors. A constructed atu2422 mutant was more virulent than the wild type bacterium; moreover, transgenic plants with a low level of Pro exhibited less severe tumor symptoms than did their wild-type parents, revealing a crucial role for Venus flytrap GABA-receptor and relative abundance of GABA and Pro in host-pathogen interaction.

Adenosine phosphonoacetic acid is slowly metabolized by NDP kinase.

NDP kinase catalyzes the last step in the phosphorylation of nucleotides. It is also involved in the activation by cellular kinases of nucleoside analogs used in antiviral therapies. Adenosine phosphonoacetic acid, a close analog of ADP already proposed as an inhibitor of ribonucleotide reductase, was found to be a poor substrate for human NDP kinase, as well as a weak inhibitor with an equilibrium dissociation constant of 0.6 mM to be compared to 0.025 mM for ADP. The X-ray structure of a complex of adenosine phosphonoacetic acid and the NDP kinase from Dictyostelium was determined to 2.0 A resolution showing that the analog adopts a binding mode similar to ADP, but that no magnesium ion is present at the active site. As ACP may also interfere with other cellular kinases, its potential as a drug targeting NDP kinase or ribonucleotide reductase is likely to be limited due to strong side effects. The design of new molecules with a narrower specificity and a stronger affinity will benefit from the detailed knowledge of the complex ACP-NDP kinase.

Crystal structures of the yeast prion Ure2p functional region in complex with glutathione and related compounds.

The [URE3] phenotype in yeast Saccharomyces cerevisiae is due to an altered prion form of Ure2p, a protein involved in nitrogen catabolism. To understand possible conformational changes at the origin of prion propagation, we previously solved the crystal structure of the Ure2p functional region [Bousset et al. (2001) Structure 9, 39-46]. We showed the protein to have a fold similar to that of the beta class of glutathione S-transferases (GSTs). Here we report crystal structures of the Ure2p functional region (extending from residues 95-354) in complex with glutathione (GSH), the substrate of all GSTs, and two widely used GST inhibitors, namely, S-hexylglutathione and S-p-nitrobenzylglutathione. In a manner similar to what is observed in many GSTs, ligand binding is not accompanied by a significant change in the conformation of the protein. We identify one GSH and one hydrophobic electrophile binding site per monomer as observed in all other GSTs. The sulfur group of GSH, that conjugates electrophiles, is located near the amide group of Asn124, allowing a hydrogen bond to be formed. Biochemical data indicate that GSH binds to Ure2p with high affinity. Its binding affects Ure2p oligomerization but has no effect on the assembly of the protein into amyloid fibrils. Despite results indicating that Ure2p lacks GST activity, we propose that Ure2p is a member of the GST superfamily that may describe a novel GST class. Our data bring new insights into the function of the Ure2p active region.

X-ray structure of HPr kinase: a bacterial protein kinase with a P-loop nucleotide-binding domain.

HPr kinase/phosphatase (HprK/P) is a key regulatory enzyme controlling carbon metabolism in Gram- positive bacteria. It catalyses the ATP-dependent phosphorylation of Ser46 in HPr, a protein of the phosphotransferase system, and also its dephosphorylation. HprK/P is unrelated to eukaryotic protein kinases, but contains the Walker motif A characteristic of nucleotide-binding proteins. We report here the X-ray structure of an active fragment of Lactobacillus casei HprK/P at 2.8 A resolution, solved by the multiwavelength anomalous dispersion method on a seleniated protein (PDB code 1jb1). The protein is a hexamer, with each subunit containing an ATP-binding domain similar to nucleoside/nucleotide kinases, and a putative HPr-binding domain unrelated to the substrate-binding domains of other kinases. The Walker motif A forms a typical P-loop which binds inorganic phosphate in the crystal. We modelled ATP binding by comparison with adenylate kinase, and designed a tentative model of the complex with HPr based on a docking simulation. The results confirm that HprK/P represents a new family of protein kinases, first identified in bacteria, but which may also have members in eukaryotes.

Structure of an XRCC1 BRCT domain: a new protein-protein interaction module.

The BRCT domain (BRCA1 C-terminus), first identified in the breast cancer suppressor protein BRCA1, is an evolutionarily conserved protein-protein interaction region of approximately 95 amino acids found in a large number of proteins involved in DNA repair, recombination and cell cycle control. Here we describe the first three-dimensional structure and fold of a BRCT domain determined by X-ray crystallography at 3.2 A resolution. The structure has been obtained from the C-terminal region of the human DNA repair protein XRCC1, and comprises a four-stranded parallel beta-sheet surrounded by three alpha-helices, which form an autonomously folded domain. The compact XRCC1 structure explains the observed sequence homology between different BRCT motifs and provides a framework for modelling other BRCT domains. Furthermore, the established structure of an XRCC1 BRCT homodimer suggests potential protein-protein interaction sites for the complementary BRCT domain in DNA ligase III, since these two domains form a stable heterodimeric complex. Based on the XRCC1 BRCT structure, we have constructed a model for the C-terminal BRCT domain of BRCA1, which frequently is mutated in familial breast and ovarian cancer. The model allows insights into the effects of such mutations on the fold of the BRCT domain.

AlF3 mimics the transition state of protein phosphorylation in the crystal structure of nucleoside diphosphate kinase and MgADP.

Nucleoside diphosphate kinase reversibly transfers the gamma-phosphate of ATP onto its active site histidine. We have investigated the transition state of histidine phosphorylation with the high-resolution crystal structures of the enzyme from Dictyostelium discoideum with MgADP and either aluminium or beryllium fluoride. The bound aluminium fluoride species is the neutral species AlF3 and not the more common AlF4-. AlF3 forms a trigonal bipyramid that makes it an accurate analog of the transition state of the gamma-phosphate of ATP undergoing transfer to the catalytic histidine. Its axial ligands are a histidine nitrogen and a beta-phosphate oxygen. Beryllium fluoride also binds at the same position and with the same ligands but in a tetrahedral geometry resembling the Michaelis complex rather than the transition state. The two x-ray structures show explicit enzyme-substrate interactions that discriminate between the ground and the transition states of the reaction. They also illustrate the partially dissociative geometry of the transition state of phosphoryl transfer and demonstrate the potential applications of metallofluorides for the study of kinase mechanisms.

The structure and functions of the HAP1/Ref-1 protein.

The HAP1/Ref-1 (hereafter referred to as HAP1) protein is a nuclear enzyme that apparently performs two distinct roles in the cellular defense against oxidative stress. One well-established role is in the repair of a variety of lesions induced in DNA either by spontaneous hydrolysis or by reactive oxygen species (ROS). This function has been characterized in great detail and the roles played by individual active site amino acid residues have been defined. The second role, which was identified only relatively recently and is still not characterized in detail, is to regulate the DNA binding activity of a group of nuclear factors. This second role proceeds via the modification of the oxidation/reduction (redox) state of a cysteine residue in the target protein, although the mechanism by which this is achieved remains to be elucidated. In this article, we shall review the latest knowledge on the relationship between structure and the dual functions of HAP1, and we will seek to explain in detail the roles played by several individual amino acid residues in the catalytic function of the HAP1 protein.

Thermal stability of hexameric and tetrameric nucleoside diphosphate kinases. Effect of subunit interaction.

The eukaryotic nucleoside diphosphate (NDP) kinases are hexamers, while the bacterial NDP kinases are tetramers made of small, single domain subunits. These enzymes represent an ideal model for studying the effect of subunit interaction on protein stability. The thermostability of NDP kinases of each class was studied by differential scanning calorimetry and biochemical methods. The hexameric NDP kinase from Dictyostelium discoideum displays one single, irreversible differential scanning calorimetry peak (Tm 62 degrees C) over a broad protein concentration, indicating a single step denaturation. The thermal stability of the protein was increased by ADP. The P105G substitution, which affects a loop implicated in subunit contacts, yields a protein that reversibly dissociates to folded monomers at 38 degrees C before the irreversible denaturation occurs (Tm 47 degrees C). ADP delays the dissociation, but does not change the Tm. These data indicate a "coupling" of the quaternary structure with the tertiary structure in the wild-type, but not in the mutated protein. We describe the x-ray structure of the P105G mutant at 2.2-A resolution. It is very similar to that of the wild-type protein. Therefore, a minimal change in the structure leads to a dramatic change of protein thermostability. The NDP kinase from Escherichia coli behaves like the P105G mutant of the Dictyostelium NDP kinase. The detailed study of their thermostability is important, since biological effects of thermolabile NDP kinases have been described in several organisms.

X-ray structure of human nucleoside diphosphate kinase B complexed with GDP at 2 A resolution.

BACKGROUND: Nucleoside diphosphate (NDP) kinases provide precursors for DNA and RNA synthesis. In mammals, these enzymes are also involved in cell regulations. Human NDP kinase B, product of the human nm23-H2 gene, is both an enzyme and a transcription factor. It activates transcription of the c-myc oncogene independently of its catalytic function, by binding to its promoter DNA. How do the two functions coexist? RESULTS: Recombinant human NDP kinase B was co-crystallized with GDP. The X-ray structure was solved at 2.0 A resolution by molecular replacement from the homologous Drosophila Awd protein. Both enzymes are homo-hexamers with a characteristic beta alpha beta beta alpha beta fold. GDP binds near the active site His118. The guanine base is in a surface cleft and interacts with the C terminus of another subunit. CONCLUSIONS: The beta alpha beta beta alpha beta fold, also present in the 'palm' domain of Escherichia coli DNA polymerase I and HIV reverse transcriptase, is both a mononucleotide- and a polynucleotide-binding fold. If NDP kinase B binds DNA in the same way as the polymerases, the enzyme must undergo a conformation change in order to carry out gene activation.

Adenosine 5'-diphosphate binding and the active site of nucleoside diphosphate kinase.

The X-ray structure of nucleoside diphosphate kinase (NDP kinase) from the slime mold Dictyostelium discoideum has been determined to 2.2-A resolution and refined to an R-factor of 0.19 with and without bound ADP-Mg2+. The nucleotide binds near His 122, a residue which becomes phosphorylated during the catalytic cycle. The mode of binding is different from that observed in other phosphokinases, and it involves no glycine-rich sequence. The adenine base makes only nonpolar contacts with the protein. It points outside, explaining the lack of specificity of NDP kinase toward the base. The ribose 2'- and 3'-hydroxyls and the pyrophosphate moiety are H-bonded to polar side chains. A Mg2+ ion bridges the alpha- to the beta-phosphate which approaches the imidazole group of His 122 from the N delta side. The geometry at the active site in the ADP-Mg2+ complex suggests a mechanism for catalysis whereby the gamma-phosphate of a nucleoside triphosphate can be transferred onto His 122 with a minimum of atomic motion.

Crystal structure of the Awd nucleotide diphosphate kinase from Drosophila.

BACKGROUND: Nucleotide diphosphate kinase (NDP kinase) is a phosphate transfer enzyme involved in cell regulation and in animal development. Drosophila NDP kinase is the product of the abnormal wing disc (awd) developmental gene, a point mutation in which can produce the killer of prune (K-pn) conditional lethal phenotype. The highly homologous mammalian genes control metastasis and a human NDP kinase acts as a transcription factor. RESULTS: The X-ray structure of the Awd protein prepared from Drosophila was solved at 2.4 A resolution by molecular replacement from the homologous Dictyostelium protein. Both are hexamers, and both have the same fold and the same active site. Subunit contacts differ as a result of sequence changes in the carboxy-terminal segment and in the loop that is the site of the K-pn mutation. CONCLUSIONS: Regulatory properties of animal NDP kinases depend on interactions with other macromolecules, such as DNA and the product of the Drosophila prune gene. The Awd structure suggests an allosteric mechanism of action of NDP kinase where DNA is the effector and the protein undergoes a major conformational change, possibly dissociating to dimers.

Renal function conscious one kidney-one clip hypertensive rats. Effect on indomethacin

Los presentes experimentos han analizado: a) la Presión Arterial (PA) y la función renal en ratas un riñón-un clip (IRIC) dos semanas después de la estenosis arterial; b) efecto de la inhibición de la ciclooxigenasa (CO) sobre la PA y la regluación de la función renal durante el período hipertensivo. Se estudiaron tres grupos de ratas utilizando animales sin anestesia, con libertad de movimiento y crónicamente instrumentados: grupo "Sham" (con operación simulada), Clip 0.31mm de luz, Clip 0.29mm de luz. Los animales fueron examinados antes (período Control) y durante la infusión de indometacina (IND, 5 mg/Kg por la cánula aórtica, n = 11 en cada grupo). La efectiva inhibición de la CO por IND fue confirmada por la determinación de prostaglandín E2 (PGE) en orina. La PA Control (mmH, media ñ ES) difirió significativamente entre los grupos (P < 0.001): Sham, 114 ñ 3; Clip 0.31, l35 ñ 2; Clip 0.29, 154 ñ 4 y los valores no variaron la infusión de IND, sugiriendo que la participación de los eicosanoides derivados de la CO, particularmente la PGE2, en la regulación de la hemodinamia renal de las ratas sham e hipertensas no es significativa. La excreción de sodio fue menor en el período Control de las ratas Clip 0.29 (P<0.01). El significativo efecto natriurético observado en este grupo Clip 0.29 por la infusión de IND sugiere la contribución de um metabolito del AA para el manejo renal del sodio en la hipertensión renovascular más severa

X-ray structure of nucleoside diphosphate kinase.

The X-ray structure of a point mutant of nucleoside diphosphate kinase (NDP kinase) from Dictyostelium discoideum has been determined to 2.2 A resolution. The enzyme is a hexamer made of identical subunits with a novel mononucleotide binding fold. Each subunit contains an alpha/beta domain with a four stranded, antiparallel beta-sheet. The topology is different from adenylate kinase, but identical to the allosteric domain of Escherichia coli ATCase regulatory subunits, which bind mononucleotides at an equivalent position. Dimer contacts between NDP kinase subunits within the hexamer are similar to those in ATCase. Trimer contacts involve a large loop of polypeptide chain that bears the site of the Pro----Ser substitution in Killer of prune (K-pn) mutants of the highly homologous Drosophila enzyme. Properties of Drosophila NDP kinase, the product of the awd developmental gene, and of the human enzyme, the product of the nm23 genes in tumorigenesis, are discussed in view of the three-dimensional structure and of possible interactions of NDP kinase with other nucleotide binding proteins.

Water and exchangeable sodium in Goldblatt two-kidney, two-clip hypertensive rats.

Exchangeable 22Na (ExNa), total body water (TBW) and the inulin space (InSp) were determined in two-kidney, two-clip (2K-2C) hypertensive and sham operated (normotensive) control rats 6-8 weeks after surgery. TBW (ml/kg lean body weight) was the same in hypertensive and sham rats. In contrast, ExNa (mEq/kglbw) and InSp (ml/kglbw) significantly increased (p less than 0.01) in rats whose hypertension did not exceed 170 mmHg. Consequently, sham, moderate hypertensive (less than 170 mmHg) and severe hypertensive (less than 170 mmHg) animals showed equal TBW but differed in body water distribution in that moderately hypertensive animals displayed a redistribution of water in favor of the extracellular space.

Initial mechanisms in hypertension after bilateral renal ischemia in the rat.

Cumulative water- and electrolyte balance, plasma creatinine (PC), plasma renin activity (PRA), urinary prostaglandins (PGs) E2, and F2alpha and kallikrein (K) were studied in 40 male Wistar CHbb THOM rats (250 +/- 4 g SE). A solid silver clip (0.25 mm lumen) was applied to both renal arteries in 18 animals; 13 rats were sham-operated and nine remained intact. The analyses were performed during a control period and up to 10 days after surgery. Blood pressure (BP) recorded on the 10th and 12th day of the study increased significantly in clipped rats with respect to sham rats (p less than 0.001);PC and PRA measured on the 11th day were not significantly different. A positive cumulative water "balance" )p less than 0.01) and sodium balance (p less than 0.02) was found in clipped rats when compared with sham rats in the first 5 days of the experimental period. Significantly higher values of PGE2 urinary excretion were observed in sham rats vs clipped rats on the 2nd and 5th day after surgery (p less than 0.02). On the 2nd day after surgery, K urinary excretion was significantly lower in clipped rats than in sham rats (p less than 0.02). No significant changes were observed in PGF2alpha excretion. The absence of significant difference in PRA 10 days after bilateral renal artery stenosis points to a lack of any fundamental role of circulating angiotensin II at this stage of the development of hypertension. The significant water- and salt retention in the first 5 days after clipping suggests that it might be involved in the pathogenesis of this model. Early changes in PGs E2 and F2alpha and K appear to be related more to intrarenal adjustments soon after surgery than to the increase in BP.